ownCloud is a widely used open-source platform designed for file synchronization, sharing, and collaboration. It allows organizations to host their own cloud storage, ensuring data sovereignty and compliance with privacy regulations. 

Its flexibility and rich feature set have made it popular among enterprises and individual users alike. 

However, as with any software, vulnerabilities can emerge, and in late 2023, a critical security flaw – CVE-2023-49103 – was discovered in its Graph API application. This flaw could allow unauthorized access to sensitive configuration details, such as admin passwords, mail server credentials, and license keys.

The risk is especially severe for organizations using ownCloud in containerized environments, where environment variables may be exposed. Let’s break down the vulnerability, its impact, and mitigation steps.

Details of the vulnerability

The vulnerability resides in the graphapi application of ownCloud. It leverages a third-party library file, GetPhpInfo.php, which calls the PHP phpinfo() function. This function, while commonly used for debugging, outputs detailed information about the server’s PHP configuration. 

In containerized deployments, environment variables – which often include sensitive information – are exposed, posing a severe security risk.

Docker-based deployments of ownCloud are particularly susceptible, as Docker containers often rely on environment variables to pass sensitive information like database credentials and API keys during runtime. Attackers exploiting this vulnerability can use the phpinfo() output to capture these details, potentially compromising the entire containerized setup.

Even disabling the graphapi app doesn’t fully mitigate the issue, as the vulnerable file remains accessible unless explicitly removed.

Impact of CVE-2023-49103

When exploited, this vulnerability allows attackers to extract sensitive information without requiring authentication. The exposed data could include:

• ownCloud administrator passwords
• Mail server credentials
• Database credentials
• ownCloud license key

Such information disclosures could lead to data breaches, unauthorized access to critical systems, and further exploitation of the organization’s infrastructure.

Exploitation in the wild

This vulnerability has been actively exploited, highlighting the urgency for remediation. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added CVE-2023-49103 to its Known Exploited Vulnerabilities (KEV) Catalog, emphasizing the need for immediate action by affected organizations.

Steps to mitigate the vulnerability

If your organization uses ownCloud, the following steps are advised to mitigate the risk posed by CVE-2023-49103:

Update the Graph API application
Upgrade to version 0.3.1 or later of the graphapi app. The updated version removes the vulnerable GetPhpInfo.php file, addressing the root cause of the issue.

Remove the vulnerable file
If upgrading isn’t immediately possible, manually delete the file located at:
owncloud/apps/graphapi/vendor/microsoft/microsoft-graph/tests/GetPhpInfo.php

Disable the phpinfo() function
Modify your PHP configuration to disable the phpinfo() function. This precaution reduces the risk of similar vulnerabilities in the future.

Change all exposed credentials
Immediately rotate any credentials that may have been exposed, including:

• Admin passwords
• Mail server logins
• Database credentials
• API and storage keys

Secure Docker environments

• For Docker-based deployments, use secret management tools like Docker Secrets or HashiCorp Vault to handle sensitive data instead of relying on environment variables.
• Limit access to containerized services and ensure proper network segmentation.
• Regularly scan Docker images for vulnerabilities and keep them updated.

Keep your ownCloud server updated

Ensure your ownCloud instance is running the latest server version, as updates often include critical security patches.

Proactive security measures

While addressing CVE-2023-49103 is essential, organizations should adopt broader security measures to prevent similar risks in the future:

Conduct regular security audits
Routine assessments can identify vulnerabilities before they are exploited.

Implement environment variable best practices
Minimize sensitive data stored in environment variables and use secret management tools.

Utilize web application firewalls (WAFs)
WAFs can help block unauthorized access attempts.

Train teams on security protocols
Ensure your IT teams are aware of emerging threats and understand mitigation strategies.

Recommended content

The Immersive Labs catalog includes a lab dedicated to CVE-2023-49103. This lab provides a vulnerable version of ownCloud hosted within a vulnerable Docker container.

This lab offers an in-depth understanding of the vulnerability and its associated exploit through practical, hands-on experience. You’ll exploit the vulnerable instance to gain access to sensitive information,  allowing you unauthorized access to the system as a privileged user.

Conclusion

CVE-2023-49103 underscores the importance of proactive security measures in software deployment. For organizations leveraging ownCloud, this vulnerability serves as a reminder to maintain vigilance, regularly update systems, and adopt comprehensive security practices.

By promptly addressing the issue and implementing the recommended mitigations, organizations can safeguard their sensitive data and reduce the likelihood of compromise.

Share your thoughts

If this vulnerability impacted your organization, what steps did you take to fix it, and what changes have you made to prevent future issues?